How hormones work HBS 3A

Hormones change the function of cells Hormones enter cells and then change the metabolic activity by one of three ways Activating certain genes in a nucleus so the cell starts making a particular protein – this could be an enzyme or a structural component Changing the shape of an enzyme to activate or inactivate it (turn it on or off) Changing the rate of protein production (in the nucleus or at the ribosomes) so changing the amount of enzyme or other proteins present

Enzyme amplification Each hormone activates thousands of enzymes The hormone triggers a number of reactions at each stage of the metabolic pathway it affects – setting of a cascade of reactions A very small amount of hormone can result in large changes or effects

Hormone clearance Some hormones are broken down by enzymes in the target cells Many hormones are broken down by the liver or kidneys Most broken down hormones are excreted by the kidneys

Types of hormones The main types of hormones are Steroid eg cortisol, aldosterone, oestrogen, progesterone, testosterone Amine eg adrenaline, noradrenaline, thyroxine, Peptide eg growth hormone, LH, FSH, ACTH, TSH, prolactin, ADH, oxytocin, insulin, glucagon, calcitonin, parathyroid hormone, hypothalamus releasing factors

Hormone action Steroid hormones pass through cell membranes and act directly on the nucleus

Hormone action 1 Non- Steroid hormones can not pass directly through cell membranes and act by secondary messengers